Work is proposed on a series of projects designed to provide information on the molecular events that occur during the multiplication of both lytic and tumor viruses. Among these projects are an investigation of the nature of the lesions in a series of temperature- sensitive mutants of reovirus, studies on the structure of reovirus RNA, and attempts to obtain reovirus transcriptase and replicase in the template-free state; an investigation of the mode of synthesis and function of poly A sequences at the 3'-ends of messenger RNAs; studies on the mechanism of action and mode of induction of interferon; and studies on the structure of rousvirus genomes, the nature of the rousvirus-coded gene product that is responsible for maintenance of the transformed state, and on the plasma membrane changes that occur when cells are morphologically transformed by rousviruses.